CAT 



CAT 



pension, whether the points be horizon- 

 tal or not. The nature of this curve was 

 Sought after in Galileo's time, but not 

 discovered till the year 1690, when Mr. 

 Bernoulli published it as a problem. Dr. 

 Gregory, in 1697, published a method of 

 investigation of the properties formerly 

 discovered by Mr. Bernoulli and Mr. 

 Leibnitz, together with some new pro- 

 perties of this curve. From him we 

 take the following method of finding the 

 general property of the catenaria. 



1. Suppose a line heavy and flexible, 

 the two extremes of which F and D, 

 Plate II. Miscellanies, fig. 8, are firmly 

 fixed in those points; by its weight it is 

 bent into a certain curve FAD, which 

 is called the catenaria. 



2. Let B D and b c be parallel to the 

 horizon, A B perpendicular to B D, and 

 D c parallel to A B, and the points B b 

 infinitely near to each other. From the 

 laws of mechanics, any three powers in 

 equilibrio are to one another as the lines 

 parallel to the lines of their direction, 

 (or inclined in any given angle) and ter- 

 minated by their mutual concourses ; 

 hence if D d express the absolute gravity 

 of the particle D d, (as it will if we allow 

 the chain to be every way uniform) then 

 D c will express that part of the gravity 

 that acts perpendicularly upon D d ; and 

 by the means of which this particle en- 

 deavours to reduce itself to a vertical 

 position ; so that if this linepla c? c be 

 constant, the perpendicular action of gra- 

 vity upon the parts of the chain will be 

 constant too, and may therefore be ex- 

 pressed by any given right line. Further, 

 the lineola D c will express the force 

 which acts against that conatus of the 

 particle D d, by which it endeavours to 

 restore itself in a position perpendicular 

 to the horizon, and hinders it from doing 

 so. This force proceeds from the pon- 

 derous line D A drawing according to 

 the direction D d ; and is, cxteris paribu^ 

 proportional to the line D A which is- the 

 cause of it. Supposing the curve FAD, 

 therefore, as before, whose vertex is A, 

 axis A B, ordinate B D, fluxion of the ax- 

 is D C=B 6, fluxion of the ordinate d c, 

 the relation of these two fluxions is thus; 

 viz. d c : D d :: a : D A curve, which is 

 the fundamental property of the curve, 

 and may be thus expressed (putting 

 A B ==a: and BD=*?/ and AD=c 



ax 



,,=_, 



CATERPILLAR, in natural history : 

 the larvae of butterflies are universally 

 known by the name of caterpillars^ and 



are extremely various in their forms an4 

 colours, some being- smooth, others be- 

 set with either simple or ramified spines, 

 and some are observed to protrude from 

 their front, when disturbed, a pair of short 

 tentacula or feelers, somewhat analagous 

 to those of a snail. A caterpillar, when 

 grown to its full size, retires to some con- 

 venient spot, and securing itself proper- 

 ly by a small quantity of silken filaments, 

 either suspends itself by the tail, hang- 

 ing with its head downwards, or else in 

 an upright position, with the body fasten- 

 ed round the middle by a number of fila- 

 ments. It then casts oft'its caterpillar-skin, 

 and commences crysalis, in which state 

 it continues till the butterfly is ready for 

 birth, which, liberating itself from the 

 skin of the chrysalis, remains till its 

 wings, which are first short, weak, and 

 covered with moisture, are fully extend- 

 ed ; this happens in about a quarter of 'an 

 hour, when the animal suddenly quits the 

 state of inactivity to which it had been so 

 long confined, and becomes at pleasure 

 an inhabitant of the air. 



CATESB^EA, in botany, so called in 

 honour of Mark Catesby, a genus of the 

 Tetrandria Monogynia class and order. 

 Natural order of Luridae. Rubiaceje, Jus- 

 sieu. Essential character : corolla mono- 

 petalous, funnel-form, extremely long, 

 superior ; stamens within the mouth ; 

 berry polyspermous. There are but two 

 species, of which C. spinosa, lily -thorn, 

 rises with a branching stem to the height 

 of twelve feet, covered with a pale russet 

 bark ; the branches come out alternately 

 from the bottom to the top, with small 

 leaves resembling those of the box-tree, in 

 clusters all round the branches at certain 

 distances ; the flowers come out single 

 from the sides of the branches, hanging 

 downward, and are of a dull yellow co- 

 lour ; the berry is the size of a middling 

 plum, hollow within, with small angular 

 seeds. This shrub was discovered by Mr. 

 Catesby near Nassau town, in Providence, 

 one of the Bahama Islands. C. parviflo- 

 ra is a native of Jamaica. 



CATHARTICS, in medicine, are the 

 same with what are commonly called pur- 

 gatives. See MEDICINE. 



CATHEDRAL, a church wherein is a 

 bishop's see or seat. 



After the establishment of Christianity, 

 the emperors, and other great men, gave 

 large demesnes and other possessions for 

 the maintenance of the clergy ; on these 

 were built the first places of worship, 

 which were called cathedra, cathedrals, 

 sees, or seats, from the bishop and his 

 chief clergy's residence thereon. 



